U.S. patent number 10,794,456 [Application Number 15/822,960] was granted by the patent office on 2020-10-06 for continuously variable transmission including a primary pulley, a secondary pulley, a metal transmission belt, and a moving apparatus.
This patent grant is currently assigned to TOYOTA JIDOSHA KABUSHIKI KAISHA. The grantee listed for this patent is TOYOTA JIDOSHA KABUSHIKI KAISHA. Invention is credited to Kazunori Harima, Yu Inase, Fumiya Kaji, Keisuke Ninomiya, Hideaki Takahara.
![](/patent/grant/10794456/US10794456-20201006-D00000.png)
![](/patent/grant/10794456/US10794456-20201006-D00001.png)
![](/patent/grant/10794456/US10794456-20201006-D00002.png)
![](/patent/grant/10794456/US10794456-20201006-D00003.png)
![](/patent/grant/10794456/US10794456-20201006-D00004.png)
![](/patent/grant/10794456/US10794456-20201006-D00005.png)
![](/patent/grant/10794456/US10794456-20201006-D00006.png)
![](/patent/grant/10794456/US10794456-20201006-M00001.png)
![](/patent/grant/10794456/US10794456-20201006-M00002.png)
United States Patent |
10,794,456 |
Kaji , et al. |
October 6, 2020 |
Continuously variable transmission including a primary pulley, a
secondary pulley, a metal transmission belt, and a moving
apparatus
Abstract
A continuously variable transmission is configured such that a
transmission ratio continuously changes by continuously changing
widths of belt winding grooves of a primary pulley and a secondary
pulley, and includes: the primary pulley including a first fixed
sheave and a first moving sheave provided in a primary shaft; the
secondary pulley including a second fixed sheave and a second
moving sheave provided in a secondary shaft; a metal transmission
belt wound around the primary pulley and the secondary pulley; and
a moving apparatus configured to integrally move the secondary
shaft and a secondary bearing supporting the secondary shaft such
that a relative positional relationship between the first fixed
sheave and the second fixed sheave changes.
Inventors: |
Kaji; Fumiya (Susono,
JP), Takahara; Hideaki (Toyota, JP),
Ninomiya; Keisuke (Susono, JP), Harima; Kazunori
(Susono, JP), Inase; Yu (Susono, JP) |
Applicant: |
Name |
City |
State |
Country |
Type |
TOYOTA JIDOSHA KABUSHIKI KAISHA |
Toyota-shi, Aichi-ken |
N/A |
JP |
|
|
Assignee: |
TOYOTA JIDOSHA KABUSHIKI KAISHA
(Toyota-shi, JP)
|
Family
ID: |
1000005096519 |
Appl.
No.: |
15/822,960 |
Filed: |
November 27, 2017 |
Prior Publication Data
|
|
|
|
Document
Identifier |
Publication Date |
|
US 20180163827 A1 |
Jun 14, 2018 |
|
Foreign Application Priority Data
|
|
|
|
|
Dec 13, 2016 [JP] |
|
|
2016-241620 |
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F16H
9/18 (20130101); F16H 9/16 (20130101); F16H
55/52 (20130101); F16H 9/24 (20130101); F16H
9/125 (20130101); F16H 9/12 (20130101) |
Current International
Class: |
F16H
9/16 (20060101); F16H 9/24 (20060101); F16H
9/12 (20060101); F16H 55/52 (20060101); F16H
9/18 (20060101) |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
|
|
|
|
|
|
|
02036647 |
|
Mar 1990 |
|
JP |
|
2002161953 |
|
Jun 2002 |
|
JP |
|
2012-127510 |
|
Jul 2012 |
|
JP |
|
2013046367 |
|
Apr 2013 |
|
WO |
|
Other References
JP2002161953 Translation. cited by examiner.
|
Primary Examiner: Truong; Minh
Attorney, Agent or Firm: Hunton Andrews Kurth LLP
Claims
What is claimed is:
1. A continuously variable transmission comprising: a primary
pulley including a first fixed sheave fixed to a primary shaft, and
a first moving sheave rotating together with the primary shaft in
an integrated manner and relatively movable in an axial direction;
a secondary pulley including a second fixed sheave fixed to a
secondary shaft, and a second moving sheave rotating together with
the secondary shaft in an integrated manner and relatively movable
in the axial direction; a metal transmission belt wound around the
primary pulley and the secondary pulley, the metal transmission
belt being configured to continuously change a transmission ratio
by continuously changing a width of a belt winding groove of the
primary pulley and a width of a belt winding groove of the
secondary pulley; and a moving apparatus configured to integrally
move either the primary shaft and a primary bearing supporting the
primary shaft or the secondary shaft and a secondary bearing
supporting the secondary shaft such that a relative positional
relationship between the first fixed sheave and the second fixed
sheave changes, the moving apparatus being configured to change the
relative positional relationship such that a misalignment amount of
the transmission belt is reduced; wherein the relative positional
relationship is determined by a shaft-to-shaft distance between the
primary shaft and the secondary shaft, and wherein when the moving
apparatus integrally moves the secondary bearing and the secondary
shaft, the moving apparatus is configured to move the secondary
bearing and the secondary shaft in an orthogonal direction to the
axial direction of the secondary shaft by giving a force in the
orthogonal direction to the secondary bearing such that the
shaft-to-shaft distance changes, the continuously variable
transmission further comprising: a drive gear configured to rotate
together with the secondary shaft in an integrated manner; and a
driven gear meshing with the drive gear, wherein when the moving
apparatus integrally moves the secondary bearing and the secondary
shaft, the moving apparatus is configured to move the secondary
bearing and the secondary shaft to reciprocate with a predetermined
arc on a circular orbit around a rotation center of the driven gear
such that a position of a rotation center of the secondary shaft is
displaced on the circular orbit, wherein a radius of the circular
orbit is equal to a sum of a pitch radius of the drive gear and a
pitch radius of the driven gear, wherein the secondary bearing is a
rolling bearing having an outer race, wherein the moving apparatus
includes a cage, and wherein the cage is a fixed member having a
hollow shape and accommodates the outer race inside the hollow in a
movable state on the circular orbit.
2. The continuously variable transmission according to claim 1,
wherein: the moving apparatus includes a hydraulic actuator; and
the moving apparatus is configured to integrally move either the
primary shaft and the primary bearing supporting the primary shaft
or the secondary shaft and the secondary bearing supporting the
secondary shaft.
3. The continuously variable transmission according to claim 1,
wherein: the moving apparatus includes a feed screw and a driving
device; and the moving apparatus is configured to integrally move
the secondary shaft and the secondary bearing supporting the
secondary shaft when a power of the driving device is transmitted
to the feed screw.
4. The continuously variable transmission according to claim 1,
wherein: the moving apparatus is configured to integrally move
either the primary shaft and the primary bearing supporting the
primary shaft or the secondary shaft and the secondary bearing
supporting the secondary shaft when the transmission ratio is
changed.
5. A continuously variable transmission comprising: a primary
pulley including a first fixed sheave fixed to a primary shaft, and
a first moving sheave rotating together with the primary shaft in
an integrated manner and relatively movable in an axial direction;
a secondary pulley including a second fixed sheave fixed to a
secondary shaft, and a second moving sheave rotating together with
the secondary shaft in an integrated manner and relatively movable
in the axial direction; a metal transmission belt wound around the
primary pulley and the secondary pulley, the metal transmission
belt being configured to continuously change a transmission ratio
by continuously changing a width of a belt winding groove of the
primary pulley and a width of a belt winding groove of the
secondary pulley; and a moving apparatus configured to integrally
move at least one of a first member supporting the primary shaft
and a second member supporting the secondary shaft such that a
relative positional relationship between the first fixed sheave and
the second fixed sheave changes, the first member being the primary
shaft and a primary bearing, the second member being the secondary
shaft and a secondary bearing, the moving apparatus being
configured to change the relative positional relationship such that
a misalignment amount of the transmission belt is reduced; wherein
the relative positional relationship is determined by a
shaft-to-shaft distance between the primary shaft and the secondary
shaft, and wherein when the moving apparatus integrally moves the
secondary bearing and the secondary shaft, the moving apparatus is
configured to move the secondary bearing and the secondary shaft in
an orthogonal direction to the axial direction of the secondary
shaft by giving a force in the orthogonal direction to the
secondary bearing such that the shaft-to-shaft distance changes,
the continuously variable transmission further comprising: a drive
gear configured to rotate together with the secondary shaft in an
integrated manner; and a driven gear meshing with the drive gear,
wherein when the moving apparatus integrally moves the secondary
bearing and the secondary shaft, the moving apparatus is configured
to move the secondary bearing and the secondary shaft to
reciprocate with a predetermined arc on a circular orbit around a
rotation center of the driven gear such that a position of a
rotation center of the secondary shaft is displaced on the circular
orbit, wherein a radius of the circular orbit is equal to a sum of
a pitch radius of the drive gear and a pitch radius of the driven
gear, wherein the secondary bearing is a rolling bearing having an
outer race, wherein the moving apparatus includes a cage, and
wherein the cage is a fixed member having a hollow shape and
accommodates the outer race inside the hollow in a movable state on
the circular orbit.
Description
INCORPORATION BY REFERENCE
The disclosure of Japanese Patent Application No. 2016-241620 filed
on Dec. 13, 2016 including the specification, drawings and abstract
is incorporated herein by reference in its entirety.
BACKGROUND
1. Technical Field
The present disclosure relates to a continuously variable
transmission.
2. Description of Related Art
A belt-type continuously variable transmission includes a variable
pulley and a belt. Japanese Patent Application Publication No.
2012-127510 (JP 2012-127510 A) describes that, in a belt-type
continuously variable transmission configured such that a belt is
wound around a pair of variable pulleys, an angular difference is
provided between a rotating shaft of a primary pulley and a
rotating shaft of a secondary pulley, so as to restrain
misalignment of the belt.
SUMMARY
However, in the configuration described in JP 2012-127510 A, a
direction of an element is changed due to a frictional force
generated between the element and a ring, which constitute the
belt. As a result, a stress concentrates on a contact part between
the elements, which might decrease durability and increase power
loss.
The present disclosure restrains misalignment of a belt and
restrains a decrease of durability and an increase of power
loss.
A first aspect of the present disclosure is a continuously variable
transmission. The continuously variable transmission includes a
primary pulley, a secondary pulley, a metal transmission belt, and
a moving apparatus. The primary pulley includes a first fixed
sheave fixed to a primary shaft, and a first moving sheave rotating
together with the primary shaft in an integrated manner and
relatively movable in an axial direction. The secondary pulley
includes a second fixed sheave fixed to a secondary shaft, and a
second moving sheave rotating together with the secondary shaft in
an integrated manner and relatively movable in the axial direction.
The transmission belt is wound around the primary pulley and the
secondary pulley. The metal transmission belt is configured to
continuously change a transmission ratio by continuously changing a
width of a belt winding groove of the primary pulley and a width of
a belt winding groove of the secondary pulley. The moving apparatus
is configured to integrally move either the primary shaft and a
primary bearing supporting the primary shaft or the secondary shaft
and a secondary bearing supporting the secondary shaft such that a
relative positional relationship between the first fixed sheave and
the second fixed sheave changes. The moving apparatus is configured
to change the relative positional relationship such that a
misalignment amount of the transmission belt is reduced.
With the above configuration, the moving apparatus can integrally
move either the primary shaft and the primary bearing or the
secondary shaft and the secondary bearing such that the relative
positional relationship between the fixed sheave of the primary
pulley and the fixed sheave of the secondary pulley changes.
Hereby, it is possible to change a shaft-to-shaft distance between
the primary shaft and the secondary shaft, or a
sheave-surface-to-sheave-surface distance between the fixed sheaves
of the pulleys, so as to reduce a misalignment amount of the
transmission belt. This makes it possible to reduce the
misalignment amount of the transmission belt, thereby making it
possible to restrain the misalignment of the transmission belt and
to restrain a decrease of durability and an increase of power
loss.
In the continuously variable transmission, the relative positional
relationship may be determined by a shaft-to-shaft distance between
the primary shaft and the secondary shaft. When the moving
apparatus integrally moves the secondary bearing and the secondary
shaft, the moving apparatus may be configured to move the secondary
bearing and the secondary shaft in an orthogonal direction to the
axial direction of the secondary shaft by giving a force in the
orthogonal direction to the secondary bearing such that the
shaft-to-shaft distance changes.
With the above configuration, the moving apparatus can move the
secondary shaft in the direction orthogonal to the axial direction.
Hereby, it is possible to change the shaft-to-shaft distance
between the primary shaft and the secondary shaft, so as to reduce
the misalignment amount of the transmission belt.
The continuously variable transmission may further include a drive
gear configured to rotate together with the secondary shaft in an
integrated manner, and a driven gear meshing with the drive gear.
When the moving apparatus integrally moves the secondary bearing
and the secondary shaft, the moving apparatus may be configured to
move the secondary bearing and the secondary shaft to reciprocate
with a predetermined arc on a circular orbit around a rotation
center of the driven gear such that a position of a rotation center
of the secondary shaft is displaced on the circular orbit. A radius
of the circular orbit may be equal to a sum of a pitch radius of
the drive gear and a pitch radius of the driven gear.
With the above configuration, it is possible to move the secondary
shaft such that the position of the rotation center of the
secondary shaft is displaced on the circular orbit around the
rotation center of the driven gear. Hereby, at the time when the
secondary shaft moves, it is possible to restrain an increase of a
meshing error in a meshing portion between the drive gear and the
driven gear. Accordingly, it is possible to restrain the
misalignment of the transmission belt and to restrain the decrease
of durability of the transmission belt and the increase of power
loss.
In the continuously variable transmission, the secondary bearing
may be a rolling bearing having an outer race that is in a shape
along the predetermined arc. The moving apparatus may include a
cage. The cage may be a fixed member having a hollow shape along
the predetermined arc, and may accommodate the outer race inside
the hollow in a movable state on the circular orbit.
With the above configuration, the arc-shaped hollow shape of the
cage of the moving apparatus allows the secondary bearing
accommodated inside the cage to move in a direction along the
predetermined arc on the circular orbit. This can restrain the
position of the rotation center of the secondary shaft from
deviating from the circular orbit. Hereby, it is possible to
restrain the increase of the meshing error in the meshing portion
between the drive gear and the driven gear and to restrain the
increase of power loss.
In the continuously variable transmission, the relative positional
relationship may be determined by a
sheave-surface-to-sheave-surface distance between a sheave surface
of the first fixed sheave and a sheave surface of the second fixed
sheave. When the moving apparatus integrally moves the primary
bearing and the primary shaft, the moving apparatus may be
configured to move the primary bearing and the primary shaft in the
axial direction of the primary shaft by giving a force in the axial
direction to the primary bearing such that the
sheave-surface-to-sheave-surface distance changes.
With the above configuration, the moving apparatus can move the
primary shaft in the axial direction. Accordingly, it is possible
to change the sheave-surface-to-sheave-surface distance between the
first fixed sheave of the primary pulley and the second fixed
sheave of the secondary pulley, so as to reduce the misalignment
amount of the transmission belt.
With the above configuration, it is possible to change the relative
positional relationship between the first fixed sheave of the
primary pulley and the second fixed sheave of the secondary pulley
by the moving apparatus. This changes the shaft-to-shaft distance
between the primary shaft and the secondary shaft, or the
sheave-surface-to-sheave-surface distance between the fixed
sheaves, thereby making it possible to reduce the misalignment
amount of the transmission belt. Accordingly, it is possible to
restrain the misalignment of the transmission belt and to restrain
the decrease of durability of the transmission belt and the
increase of power loss.
In the continuously variable transmission, the moving apparatus may
include a hydraulic actuator. The moving apparatus may be
configured to integrally move either the primary shaft and the
primary bearing supporting the primary shaft or the secondary shaft
and the secondary bearing supporting the secondary shaft when a
hydraulic pressure of the hydraulic actuator reaches a hydraulic
pressure corresponding to the transmission ratio.
In the continuously variable transmission, the moving apparatus may
include a feed screw and a driving device. The moving apparatus may
be configured to integrally move the secondary shaft and the
secondary bearing supporting the secondary shaft when a power of
the driving device is transmitted to the feed screw.
In the continuously variable transmission, the moving apparatus may
be configured to integrally move either the primary shaft and the
primary bearing supporting the primary shaft or the secondary shaft
and the secondary bearing supporting the secondary shaft when the
transmission ratio is changed.
A second aspect of the present disclosure is a continuously
variable transmission. The continuously variable transmission
includes a primary pulley, a secondary pulley, a metal transmission
belt, and a moving apparatus. The primary pulley includes a first
fixed sheave fixed to a primary shaft, and a first moving sheave
rotating together with the primary shaft in an integrated manner
and relatively movable in an axial direction. The secondary pulley
includes a second fixed sheave fixed to the secondary shaft, and a
second moving sheave rotating together with the secondary shaft in
an integrated manner and relatively movable in the axial direction.
The transmission belt is wound around the primary pulley and the
secondary pulley. The metal transmission belt is configured to
continuously change a transmission ratio by continuously changing a
width of a belt winding groove of the primary pulley and a width of
a belt winding groove of the secondary pulley. The moving apparatus
is configured to integrally move at least one of a first member
supporting the primary shaft and a second member supporting the
secondary shaft such that a relative positional relationship
between the first fixed sheave and the second fixed sheave changes.
The first member is the primary shaft and a primary bearing. The
second member is the secondary shaft and a secondary bearing. The
moving apparatus is configured to change the relative positional
relationship such that a misalignment amount of the transmission
belt is reduced.
BRIEF DESCRIPTION OF THE DRAWINGS
Features, advantages, and technical and industrial significance of
exemplary embodiments of the disclosure will be described below
with reference to the accompanying drawings, in which like numerals
denote like elements, and wherein:
FIG. 1 is a skeleton diagram schematically illustrating a power
transmission mechanism of a vehicle provided with a belt-type
continuously variable transmission;
FIG. 2 is a view to describe an overall length of a belt;
FIG. 3 is a view to describe a misalignment amount of the belt;
FIG. 4 is a view to describe a circular orbit;
FIG. 5 is a view schematically illustrating an example of a moving
apparatus;
FIG. 6 is a view schematically illustrating a modification of the
moving apparatus;
FIG. 7 is a view schematically illustrating another modification of
the moving apparatus;
FIG. 8 is a view schematically illustrating a driving device of the
moving apparatus illustrated in FIG. 7; and
FIG. 9 is a view schematically illustrating an example of the
moving apparatus provided on a primary shaft side.
DETAILED DESCRIPTION OF EMBODIMENTS
A belt-type continuously variable transmission in an embodiment of
the present disclosure will be described more specifically with
reference to the drawings.
FIG. 1 is a skeleton diagram schematically illustrating a power
transmission mechanism of a vehicle provided with the belt-type
continuously variable transmission. As illustrated in FIG. 1, a
vehicle Ve includes an engine (Eng) 1 as a power source. A power
output from the engine 1 is input into a belt-type continuously
variable transmission (hereinafter just referred to as "CVT") 5 via
a torque converter (T/C) 2, a forward/reverse changing mechanism 3,
and an input shaft 4, and then transmitted from the CVT 5 to a
counter gear mechanism (a reduction gear) 8, a differential
mechanism 9, axles 10, and driving wheels 11 via an output shaft 6
and an output gear 7.
The torque converter 2 is connected to the forward/reverse changing
mechanism 3 via a turbine shaft 2a in a power transmittable manner.
The forward/reverse changing mechanism 3 is a mechanism configured
to selectively change a rotation direction of the input shaft 4
between the same direction as a rotation direction of the turbine
shaft 2a and an opposite direction to the rotation direction of the
turbine shaft 2a. For example, the forward/reverse changing
mechanism 3 is constituted by a planetary gear mechanism and a
plurality of engaging devices. The forward/reverse changing
mechanism 3 is connected to the CVT 5 via the input shaft 4 in a
power transmittable manner.
The CVT 5 includes a primary pulley 20, which is a first variable
pulley, a secondary pulley 30, which is a second variable pulley,
and a transmission belt (hereinafter just referred to as a "belt")
40 wound around belt winding grooves formed in the pulleys 20, 30.
The primary pulley 20 rotates together with the input shaft 4 in an
integrated manner. The secondary pulley 30 rotates together with
the output shaft 6 in an integrated manner. In the example
illustrated in FIG. 1, a primary shaft 20a, which is a rotating
shaft of the primary pulley 20, is constituted by the input shaft
4. Further, a secondary shaft 30a, which is a rotating shaft of the
secondary pulley 30, is constituted by the output shaft 6.
The primary pulley 20 includes a fixed sheave 21 fixed to the
primary shaft 20a, a moving sheave 22, which can relatively move in
an axial direction on the primary shaft 20a, and a first hydraulic
chamber 23 configured to give a thrust to the moving sheave 22.
Since the moving sheave 22 is splined to the primary shaft 20a, the
moving sheave 22 rotates together with the primary shaft 20a in an
integrated manner. The belt winding groove (hereinafter referred to
as a "V-groove") of the primary pulley 20 is constituted by a
sheave surface 21a of the fixed sheave 21 and a sheave surface 22a
of the moving sheave 22. Further, the first hydraulic chamber 23 is
placed on a back-face side (a side opposite to the sheave surface
22a) of the moving sheave 22, and generates a force (thrust) to
press the moving sheave 22 in the axial direction toward the fixed
sheave 21 side by a hydraulic pressure. The moving sheave 22 moves
in the axial direction due to the thrust, so that a width of the
V-groove of the primary pulley 20 changes.
Further, the primary shaft 20a and the primary pulley 20 are
rotatably supported by a primary bearing 50 with respect to a case
(not shown). The primary bearing 50 is a rolling bearing, and
includes a pair of primary bearings 51, 52 placed on both sides of
the primary pulley 20 in the axial direction. Respective inner
races of the primary bearings 51, 52 are attached to the primary
shaft 20a, and respective outer races thereof are attached to the
case. One primary bearing 51 is placed on an opposite side to the
forward/reverse changing mechanism 3 across the primary pulley 20
in the axial direction. The other primary bearing 52 is placed
between the primary pulley 20 and the forward/reverse changing
mechanism 3 in the axial direction.
The secondary pulley 30 includes a fixed sheave 31 fixed to the
secondary shaft 30a, a moving sheave 32, which can relatively move
in the axial direction on the secondary shaft 30a, and a second
hydraulic chamber 33 configured to give a thrust to the moving
sheave 32. Since the moving sheave 32 is splined to the secondary
shaft 30a, the moving sheave 32 rotates together with the secondary
shaft 30a in an integrated manner. The V-groove of the secondary
pulley 30 is constituted by a sheave surface 31a of the fixed
sheave 31 and a sheave surface 32a of the moving sheave 32.
Further, the second hydraulic chamber 33 is placed on a back-face
side of the moving sheave 32, and generates a force (thrust) to
press the moving sheave 32 in the axial direction toward the fixed
sheave 31 side by the hydraulic pressure. The moving sheave 32
moves in the axial direction due to the thrust, so that a width of
the V-groove of the secondary pulley 30 changes.
Further, the secondary shaft 30a and the secondary pulley 30 are
rotatably supported by a secondary bearing 60 with respect to the
case. The secondary bearing 60 is a rolling bearing, and includes a
pair of secondary bearings 61, 62 placed in both ends of the
secondary shaft 30a on both sides of the secondary pulley 30 in the
axial direction. Respective inner races of the secondary bearings
61, 62 are attached to the secondary shaft 30a, and respective
outer races 60a (illustrated in FIG. 5 and so on) thereof are
attached to the case. One secondary bearing 61 is placed on a side
opposite to the output gear 7 across the secondary pulley 30 in the
axial direction. The other secondary bearing 62 is placed on a side
opposite to the secondary pulley 30 across the output gear 7 in the
axial direction.
The belt 40 is an endless metal belt, and its belt length (overall
length) is unchangeable. For example, the belt 40 is constituted by
a belt (a so-called steel band belt) configured such that a
plurality of iron and steel elements is attached to two metal
rings, or a chain belt configured such that a plurality of metal
plates (links) is connected by a plurality of pins in an annular
shape. In a case where the belt 40 is a steel band belt, both ends
of the elements are sandwiched by the V-grooves of the pulleys 20,
30, so as to generate frictional forces between the sheave surfaces
21a, 22a, 31a, 32a. In a case where the belt 40 is a chain belt,
both ends of the pins are sandwiched by the V-grooves of the
pulleys 20, 30, so as to generate frictional forces between the
sheave surfaces 21a, 22a, 31a, 32a. That is, the belt 40 used for
the CVT 5 may be a steel band belt or a chain belt.
In the CVT 5, when the widths of the V-grooves of the pulleys 20,
30 are changed, a ratio between a radius of the belt 40 wound
around the primary pulley 20 (hereinafter referred to as a
"primary-side belt winding radius") and a radius of the belt 40
wound around the secondary pulley 30 (hereinafter referred to as a
"secondary-side belt winding radius") changes continuously. That
is, a transmission ratio .gamma. of the CVT 5 can change
continuously.
Further, when a speed control to change the transmission ratio
.gamma. of the CVT 5 is performed, a hydraulic pressure in the
first hydraulic chamber 23 on the primary side is controlled so as
to change the belt winding radiuses of the pulleys 20, 30, and a
hydraulic pressure in the second hydraulic chamber 33 on the
secondary side is controlled so as to control a belt clamping
pressure of the CVT 5 to an appropriate magnitude. The belt
clamping pressure is a force to clamp the belt 40 from both sides
in the axial direction by the sheave surface 21a, 31a on a fixed
side and the sheave surface 22a, 32a on a moving side in each
pulley 20, 30. When the belt clamping pressure is controlled to an
appropriate magnitude, an optimum frictional force is generated
between the V-grooves of the pulleys 20, 30 and the belt 40, so
that a belt tension between the pulleys 20, 30 is secured. A power
changed in the CVT 5 is output from the output gear 7 rotating
together with the output shaft 6 in an integrated manner.
The output gear 7 meshes with a counter driven gear 8a of the
counter gear mechanism 8. That is, a gear pair is formed by the
output gear 7, which is a drive gear, and the counter driven gear
8a, which is a driven gear. The counter gear mechanism 8 is a
deceleration mechanism configured such that the counter driven gear
8a, a counter drive gear 8b, and a counter shaft 8c rotate together
in an integrated manner. The counter drive gear 8b meshes with a
differential ring gear 9a of the differential mechanism 9. Right
and left driving wheels 11, 11 are connected to the differential
mechanism 9 via right and left axles 10, 10.
In the power transmission mechanism thus configured, the fixed
sheaves 21, 31 of the CVT 5 are placed at diagonal positions (on
opposite sides in the axial direction across the belt 40 and on
different axes). Accordingly, the belt 40 moves to the same
direction along the axial direction relative to the fixed sheaves
21, 31 at the time of a change gear operation. Hereby, misalignment
of the belt 40 should be restrained. However, the misalignment of
the belt 40 might occur geometrically (details thereof will be
described later with reference to FIGS. 2 and 3). In view of this,
in the present embodiment, in order to restrain the misalignment of
the belt 40, a moving apparatus 100 (described later more
specifically with reference to FIG. 4) that can move the pair of
secondary bearings 61, 62 supporting the secondary pulley 30 is
provided. By changing a relative positional relationship between
the fixed sheave 21 of the primary pulley 20 and the fixed sheave
31 of the secondary pulley 30 by the moving apparatus 100, it is
possible to restrain the misalignment of the belt 40 and to secure
durability of the belt 40, thereby restraining an increase of power
loss. That is, the moving apparatus 100 is configured to change the
relative positional relationship, so that a misalignment amount
.delta. of the belt 40 is reduced.
Note that, as illustrated in FIG. 1, the moving apparatus 100
includes a first moving apparatus 100A configured to move one
secondary bearing 61, and a second moving apparatus 100B configured
to move the other secondary bearing 62. Since the moving
apparatuses 100A, 100B have the same configuration, they are
described as the moving apparatus 100 when they are not
particularly distinguished. Further, when the pair of secondary
bearings 61, 62 are not particularly distinguished, they are
described as the secondary bearing 60.
Referring to FIGS. 2, 3, the misalignment of the belt 40 is
described. The misalignment of the belt 40 (hereinafter just
referred to as the "misalignment") indicates that an axial center
position of the belt 40 sandwiched by the V-groove of the primary
pulley 20 deviates in the axial direction from an axial center
position of the belt 40 sandwiched by the V-groove of the secondary
pulley 30. One of the reasons to cause the misalignment is that the
overall length (the belt length) of the belt 40 is
unchangeable.
FIG. 2 is a view to describe the overall length of the belt 40. As
illustrated in FIG. 2, the overall length (hereinafter referred to
as the "belt length") L.sub.b of the belt 40 is expressed as a sum
of a part wound around the primary pulley 20, a part wound around
the secondary pulley 30, and linear parts between the pulleys 20,
30. That is, the belt length L.sub.b can be expressed by Expression
(1). L.sub.b=2A+(.pi.+2.theta.)R.sub.p+(.pi.-2.theta.)R.sub.s
(1)
Here, A indicates a shaft-to-shaft distance between the primary
shaft 20a and the secondary shaft 30a. .theta. indicates a bite
angle of the belt 40. R.sub.p indicates the primary-side belt
winding radius (a primary-side belt pitch radius). R.sub.s
indicates the secondary-side belt winding radius (a secondary-side
belt pitch radius). Note that the shaft-to-shaft distance A is a
distance between a rotation center O.sub.p of the primary shaft 20a
and a rotation center O.sub.s of the secondary shaft 30a.
In the CVT 5, although the belt length L.sub.b is uniform, a change
amount of the primary-side belt winding radius R.sub.p does not
just become a change amount of the secondary-side belt winding
radius R.sub.s, at the time of the change gear operation. More
specifically, the change amount of the belt winding radius is
smaller in a large-diameter side than in a small-diameter side.
Accordingly, when the CVT 5 performs the change gear operation from
a speed-up state (.gamma.<1), the change amount of the
primary-side belt winding radius R.sub.p becomes smaller than the
change amount of the secondary-side belt winding radius R.sub.s. In
the meantime, when the CVT 5 performs the change gear operation
from a slowing-down state (.gamma.>1), the change amount of the
secondary-side belt winding radius R.sub.s becomes smaller than the
change amount of the primary-side belt winding radius R.sub.p. When
such a difference in the change amount of the belt winding radius
occurs between the primary side and the secondary side, a
difference occurs between an axial moving amount of the moving
sheave 22 on the primary side and an axial moving amount of the
moving sheave 32 on the secondary side. This causes the primary
side and the secondary side to have different axial center
positions (centers in the belt width) of the belt 40, which changes
the misalignment amount .delta..
FIG. 3 is a view to describe the misalignment amount .delta. of the
belt 40. The misalignment amount .delta. can be expressed by
Expression (2).
.delta..times..times..alpha..times..times..times..times..alpha..times..ti-
mes..times..alpha. ##EQU00001##
In Expression (2), .delta. indicates a misalignment amount of the
belt 40 per transmission ratio .gamma.. U indicates a
surface-to-surface orthogonal distance (hereinafter referred to as
a "sheave-surface-to-sheave-surface distance") between the sheave
surface 21a of the fixed sheave 21 of the primary pulley 20 and the
sheave surface 31a of the fixed sheave 31 of the secondary pulley
30. .alpha. indicates a sheave angle (an inclination angle of the
sheave surface 21a, 22a, 31a, 32a). B.sub.e indicates a width (an
axial length) of the belt 40. Further, "U/cos .alpha.-A tan
.alpha." indicates an axial distance between the fixed sheaves 21,
31. "(R.sub.p+R.sub.s)tan .alpha." indicates an axial moving amount
of the belt 40 along with the change of the belt winding
radius.
While the belt winding radiuses of the pulleys 20, 30 are variable,
there is a constraint that the belt length L.sub.b is unchangeable.
In terms of the constraint, when Expression (1) is solved, the
primary-side belt winding radius R.sub.p can be expressed as
Expression (3).
.pi..times..function..gamma..times..times..function..gamma..times..times.-
.times..pi..times..times..function..gamma..times..gamma.
##EQU00002##
In the present embodiment, in order to reduce the misalignment
amount .delta. expressed by Expression (2), the moving apparatus
100 is configured to change the shaft-to-shaft distance A. Further,
the moving apparatus 100 is configured to move the secondary shaft
30a on a predetermined circular orbit, so that a meshing error does
not occur in a meshing portion between the output gear 7 and the
counter driven gear 8a due to the change of the shaft-to-shaft
distance A. An example of the circular orbit is illustrated in FIG.
4.
FIG. 4 is a view to describe a circular orbit. As illustrated in
FIG. 4, a circular orbit D is a circular orbit around a rotation
center O of the counter driven gear 8a. That is, a radius of the
circular orbit D is equal to a sum of a pitch radius R1 of the
output gear 7 and a pitch radius R2 of the counter driven gear
8a.
The secondary shaft 30a is moved so that a position of a rotation
center Os of the secondary shaft 30a is displaced on the circular
orbit D by the moving apparatus 100. By moving the position of the
rotation center Os of the secondary shaft 30a on the circular orbit
D, it is possible to restrain an occurrence of a meshing error in
the meshing portion between the output gear 7 and the counter
driven gear 8a. Further, the moving apparatus 100 causes the
secondary shaft 30a to reciprocate so as to draw a locus of a
predetermined arc on the circular orbit D. Note that, in a case
where the secondary shaft 30a is moved, the position of the primary
shaft 20a is fixed.
FIG. 5 is a view schematically illustrating an example of the
moving apparatus 100. As illustrated in FIG. 5, the moving
apparatus 100 is a hydraulic actuator configured to apply a
hydraulic pressure to the secondary bearing 60 from both sides in a
circumference direction of the circular orbit D, so that the
secondary bearing 60 and the secondary shaft 30a can reciprocate
integrally on the circular orbit D.
The moving apparatus 100 includes a cage 101 having a hollow shape
in which the secondary bearing 60 is accommodated, pistons 102
configured to press the secondary bearing 60 inside the cage 101,
hydraulic chambers 103 formed inside the cage 101, and oil passages
104 configured to supply a hydraulic pressure to the hydraulic
chambers 103.
The cage 101 is a fixed member having a hollow shape and fixed to
the case, and the outer race 60a of the secondary bearing 60 is
accommodated therein in a movable state on the circular orbit D. As
illustrated in FIG. 5, the cage 101 includes an outer guide portion
101a and an inner guide portion 101b formed in an arc shape along a
circle concentric to a center (the rotation center O of the counter
driven gear 8a) of the circular orbit D. Similarly to the cage 101,
a shape of the outer race 60a of the secondary bearing 60 is formed
in an arc shape along the circle concentric to the center of the
circular orbit D. In a state where the secondary bearing 60 is
accommodated in the cage 101, the secondary bearing 60 is movable
in the circumferential direction of the circular orbit D, but is
not movable in a radial direction of the circular orbit D.
The pistons 102 are provided in the cage 101 so as to be placed on
both sides of the secondary bearing 60 in the circumference
direction of the circular orbit D. The piston 102 is configured to
be slidable on an inner surface (the outer guide portion 101a and
the inner guide portion 101b) of the cage 101 in a state where the
piston 102 seals the cage 101 with respect to the hydraulic chamber
103.
The hydraulic chambers 103 are provided on both sides of the
secondary bearing 60 in the circumference direction of the circular
orbit D, and are connected to a hydraulic circuit (not shown) via
respective oil passages 104. Further, the hydraulic pressure of the
hydraulic chamber 103 is controlled by an electronic control unit
(not shown) provided in the vehicle Ve to a hydraulic pressure
corresponding to the transmission ratio .gamma. of the CVT 5. As
described above, the misalignment amount .delta. changes according
to the transmission ratio .gamma. of the CVT5, so that the
hydraulic chamber 103 is controlled to a hydraulic pressure with a
magnitude that can reduce the misalignment amount .delta. according
to the transmission ratio .gamma.. The piston 102 is pushed by the
hydraulic pressure of the hydraulic chamber 103 controlled as such
so as to give a force (a moving force) in the circumferential
direction of the circular orbit D to the secondary bearing 60 and
the secondary shaft 30a. Note that, since the circumference
direction of the circular orbit D extends in a direction
perpendicular to the axial direction of the secondary shaft 30a, a
force in the direction perpendicular to the axial direction of the
secondary shaft 30a is applied to the secondary bearing 60 and the
secondary shaft 30a from the moving apparatus 100.
Further, when the hydraulic pressure control of the hydraulic
chamber 103 is performed in conjunction with gear shifting of the
CVT 5 at the time of the gear shifting, the speed control can be
performed in conjunction with a shaft-to-shaft distance control.
For example, by supplying a part of the hydraulic pressure
discharged from the first hydraulic chamber 23 or the second
hydraulic chamber 33 of the CVT 5 to the hydraulic chamber 103 of
the moving apparatus 100 at the time of the gear shifting, it is
possible to perform the hydraulic pressure control in conjunction
therewith.
As described above, according to the present embodiment, it is
possible to change the shaft-to-shaft distance A between the
primary shaft 20a and the secondary shaft 30a by the moving
apparatus 100. Accordingly, the shaft-to-shaft distance A can be
changed to a distance that can reduce the misalignment amount
.delta. expressed by Expression (2), thereby making it possible to
restrain misalignment in the CVT 5.
Further, an angular difference may not be provided between the
primary shaft 20a and the secondary shaft 30a, unlike the
conventional configuration, thereby making it possible to restrain
a decrease of durability of the belt 40 and an increase of power
loss in the CVT 5. Further, since the secondary shaft 30a is moved
by the moving apparatus 100 on the circular orbit D, it is possible
to restrain an increase of the meshing error in the meshing portion
between the output gear 7 and the counter driven gear 8a. Hereby,
when the secondary shaft 30a moves, it is possible to restrain the
increase of power loss that increases the meshing error of the gear
pair. Accordingly, it is possible to restrain the misalignment and
to restrain the decrease of durability and the increase of power
loss.
Note that the present disclosure is not limited to the above
embodiment, and can be changed appropriately without departing from
the object of the present disclosure.
For example, the moving apparatus 100 is not limited to the
configuration illustrated in FIG. 5. Modifications of the moving
apparatus 100 are illustrated in FIGS. 6 and 7.
FIG. 6 is a view schematically illustrating a modification of the
moving apparatus 100. As illustrated in FIG. 6, in a moving
apparatus 100 of the modification, a hydraulic chamber 103 is
provided only on one side of a secondary bearing 60 in a
circumference direction of a circular orbit D, and a spring 105 is
provided on the other side. The spring 105 is placed inside a cage
101 and is sandwiched between an inner wall surface of the cage 101
and a piston 102 in the circumference direction of the circular
orbit D. A biasing force in a direction returned to a position on
the hydraulic chamber 103 side in the circumference direction of
the circular orbit D is applied to the secondary bearing 60 from
the spring 105. As such, only one hydraulic chamber 103 should be
provided inside the cage 101, so that a hydraulic pressure control
of the hydraulic chamber 103 according to a transmission ratio
.gamma. becomes simple. Further, one oil passage 104 should be
provided, so the structure becomes also simple. Note that, although
not illustrated in the figure, a spring that applies a biasing
force in the circumferential direction of the circular orbit D may
be provided inside the hydraulic chamber 103. In this case, it is
possible to apply the biasing forces of the springs to the
secondary bearing 60 from both sides in the circumference direction
of the circular orbit D. Accordingly, it is possible to balance
(position) the secondary shaft 30a on the circular orbit D by the
biasing forces of two springs.
FIG. 7 is a view schematically illustrating another modification of
the moving apparatus 100. FIG. 8 is a view schematically
illustrating a driving device of the moving apparatus 100
illustrated in FIG. 7. As illustrated in FIG. 7, the moving
apparatus 100 of another modification includes a cage 111, a feed
screw 112, and support portions 113 attached to a tip end of the
feed screw 112. A through-hole through which the feed screw 112
penetrates is provided in a wall portion of the cage 111. The tip
end of the feed screw 112 is placed inside the cage 111, so as to
be operated by a driving device 150 (illustrated in FIG. 8). The
support portions 113 are placed on both sides of a secondary
bearing 60 in a circumference direction of a circular orbit D. The
support portion 113 is provided with a guide groove formed in a
coupling portion with the tip end of the feed screw 112, so as to
convert a force of the feed screw 112 in the axial direction into a
force in the circumference direction of the circular orbit D.
Further, the feed screw 112 is provided with a U-shaped arm portion
112a. Hereby, it is possible to give forces to the secondary
bearing 60 from the feed screw 112 toward both sides in the
circumference direction of the circular orbit D. Further, as
illustrated in FIG. 8, the driving device 150 of the moving
apparatus 100 is an electric actuator and is configured to transmit
a power of the electric motor 151 to the feed screw 112 via a
reduction gear pair constituted by a reduction gear 152 and a
driven gear 153. As such, since the moving apparatus 100 is
constituted by the electric actuator using the reduction gear pair,
it is possible to highly precisely position the position of the
secondary shaft 30a on the circular orbit D.
Further, the moving apparatus is not limited to the configuration
that can move the secondary shaft 30a, but may be configured to
move the primary shaft 20a. In short, the moving apparatus may be
configured to move the secondary shaft 30a or the primary shaft 20a
in a predetermined direction if the shaft-to-shaft distance A
expressed by Expression (2) or the sheave-surface-to-sheave-surface
distance U is changeable. An example of a moving apparatus 200
configured to move a primary shaft 20a is illustrated in FIG. 9.
Note that, in the description referring to FIG. 9, a description
about the configuration similar to the configuration described
above is omitted, and the same reference sign is used.
FIG. 9 is a view schematically illustrating an example of the
moving apparatus 200 provided on the primary pulley 20 side. First,
in a CVT 5 of the example illustrated in FIG. 9, the primary shaft
20a is formed as a different member from an input shaft 4. The
input shaft 4 and the primary shaft 20a are connected (splined) by
a spline portion 12 in an integrally rotatable manner. One primary
bearing 51 is configured to be pushed in an axial direction toward
a forward/reverse changing mechanism 3 side (the primary pulley 20
side) by a hydraulic pressure of the moving apparatus 200.
More specifically, the moving apparatus 200 includes a piston 201
configured to push the one primary bearing 51, a cylinder 202 in
which the piston 201 is provided, and a hydraulic chamber 203 in
which the cylinder 202 is provided. A hydraulic pressure is
supplied to the hydraulic chamber 203 from a hydraulic circuit (not
shown). That is, the moving apparatus 200 is a hydraulic actuator
and is configured to move the primary shaft 20a in the axial
direction by the hydraulic pressure. Further, an axial moving
amount of the primary shaft 20a can be absorbed by the spline
portion 12. That is, even if the primary shaft 20a is displaced in
the axial direction, the displacement does not affect the input
shaft 4 side. Accordingly, a position of a fixed sheave 21 on the
primary side is displaced in the axial direction, so as to change a
sheave-surface-to-sheave-surface distance U between the fixed
sheaves 21, 31 of pulleys 20, 30. This makes it possible to reduce
a misalignment amount .delta. corresponding to a transmission ratio
.gamma.. Note that, in a case where the primary shaft 20a is moved,
a position of a secondary shaft 30a is fixed.
Note that the present disclosure is not limited to the above
embodiment, and can be changed appropriately without departing from
the object of the present disclosure. For example, the CVT may
include both the moving apparatus 100 and the moving apparatus 200,
so that the primary shaft and the primary bearing supporting the
primary shaft, and the secondary shaft and the secondary bearing
supporting the secondary shaft may be moved integrally by the
moving apparatus 100 and the moving apparatus 200.
* * * * *